Solid phase extraction (SPE) is a well-established laboratory technique for analyzing liquid and mixed liquid/solid samples. The basic objective of such apparatus is to filter the solid portion of the sample (if any) and to selectively adsorb compounds from the liquid portion onto a sorbent. The analyte of interest can be subsequently extracted from the solvent and eluted from the sorbent with a minimal amount of an appropriate solvent.
Typical conventional SPE disk apparatus disposes a thin sorbent-impregnated SPE disk between the flange of an upper funnel and the flange of a lower base. Sample is poured into the funnel, and a vacuum source is applied to the base to draw sample through the disk. From time to time the vacuum source is disconnected, a number of manual manipulations and transfers are performed and extraction solvent is applied to the disk to remove analyte adsorbed within.
Unfortunately this apparatus loses analyte of interest and lacks precision. It loses analyte because of lateral wicking to the periphery of the disk and weeping out the edges. In addition, analyte can be lost through manual transfers of the solvent containing the analyte into different sample containers. It lacks precision because analyte wicked toward the periphery can be lost to analysis even if it does not reach the edges. If the material wicks into the region between the flanges, it moves out of the direct flow region where it can be extracted into an indirect flow (dead) region where it is not extracted in conventional practice. Accordingly there is a need for an improved SPE apparatus.